Surface Erosion Research Articles

Surface modified cellulose nanospheres with simultaneous nucleation and degradation-accelerating effects on poly(lactic acid)

As a novel type of nanocellulose material, cellulose nanospheres (CNSs) have gained significant attention and rapid development in recent years. In this work, the surface hydrophobic modification of CNSs was achieved by employing maleic anhydride as an esterifying agent. The effects of modified cellulose nanospheres (CNS-MA) on the crystallization and hydrolysis behaviors of polylactic acid (PLA)-based composites were systematically investigated. The results demonstrate that surface modification improves the dispersion of CNSs in the PLA matrix. Well-dispersed particles act as nucleation sites, which increases the crystallization rate and crystallinity of PLA and endows the composites with remarkable heat distortion resistance. The storage modulus of the PLA/CNS-MA composites exceeds 300 MPa, even at an elevated temperature of 90 °C. Furthermore, the hydrolytic degradation of PLA is dramatically accelerated with the addition of CNS-MA. Combining the morphology observations and theoretical calculations, it is speculated that the fast hydrolytic degradation is related to a transition in the main hydrolytic degradation mechanism from surface erosion to bulk erosion, because the presence of CNS-MA provides particular pathways for water molecules to diffuse into the interior of the composites. This research highlights the potential of CNSs as a multifunctional filler with both reinforcing and degradation-promoting effects, offering valuable insights for the study of other biomass nanomaterials.

Particle-scale kinematic model for the surface erosion of granular beds

Particle-scale kinematic model for the surface erosion of granular beds

State-of-the-Art Review of Continuum Mechanics-Based Modelling of Soil Surface Erosion

AbstractSoil surface erosion can shape the morphography of rivers and estuaries in the natural environment and induce high potential risks to structures in engineering. Numerical simulations based on continuum mechanics theory can provide reliable assessments of the evolution of surface erosion from the perspective of a large-scale view. However, current studies on continuum mechanics-based modelling are still limited. This paper comprehensively reviews such numerical simulations of soil surface erosion. This review begins by discussing the fundamental physical mechanisms of surface erosion. Subsequently, it explores the basic physics-based conservation equations controlling soils and fluids in surface erosion. Then, the empirical formulae depicting the different stages of surface erosion are presented. Building on these mathematical foundations, this paper reviews various numerical methods for surface erosion modelling from a continuum mechanics perspective. Finally, this paper discusses the advantages and limitations of the numerical methods. This work can provide researchers convenience for using numerical models on surface erosion simulations.

Subsurface Sediment Transport in the Shallow Vadose Zone of Fine‐Textured Soils With Heterogenous Preferential Flows

ABSTRACTSubsurface sediment transport in tile‐drained landscapes occurs through macropores; however, little is known regarding how heterogeneous preferential flows influence fluxes. We performed laboratory rainfall simulations on 10 intact core lysimeters from a tile‐drained field in Indiana, USA to study the impacts of surface and subsurface erosion on sediment leachate in heterogeneous preferential flow paths. Seven rainfall simulations were conducted to assess the impact of rainfall intensity on the leachate of surface eroded sediments (three events), and the impact of antecedent conditions on subsurface eroded sediments (four events). Cumulative sediment yield, linear mixed effects modelling, and hysteresis analyses were performed for all events. Results were presented in a series of four case studies. Results showed that surface sediment leachate concentration and yield were tightly linked to the filtration capacity of lysimeters, with more than 2/3rd of sediment originating from a single lysimeter, despite similar flow leachate volumes from each. Rainfall intensity significantly impacted the transport of surface eroded sediment at the highest intensity. Subsurface sediment erosion from undisturbed macropores was low compared to surface soils, but we found contrasting controls on sediment concentrations at low and high antecedent moistures that were equally important to sediment leachate yields. Disturbed macropores produced comparable sediment yields to surface erosion and behaved similarly to soil pipes in terms of erosion mechanics. Hysteresis results generally highlighted contrasting results for surface and subsurface sources but suggest that the prominence of slow flow, low‐concentration leachate sources can alter the interpretation of results in field‐scale applications. Our findings underscore an array of processes and pathways for sediment transport in the shallow vadose zone, and results will be useful for evaluating new model formulations.

3D digital holography for measuring particle impact crater morphology and in-situ analysis of oxidation healing on steel surfaces

Deformation and erosion of steel due to particle impacts in high-temperature environments are common issues in industrial applications. Under high-temperature conditions, an oxide layer forms that affects the deformation and erosion of the steel surface following particle impacts. Studying the interaction mechanism of oxidation and deformation (erosion) is of considerable significance. Traditional research methods primarily involve ex-situ measurements on samples post-erosion and oxidation, which cannot capture the morphological changes of the steel surface immediately following particle impact. Utilizing 3D digital holography (DH) technology, this paper develops a measurement system to investigate the surface morphological changes in steel induced by single particle impacts. We utilized this experimental system to measure the impact crater morphology of 500 μm zirconia particles impacting Q690 steel sheets. Our findings indicate that Hertzian ring cracks formation is significantly affected by heating temperature and impact angle. Notably, oxide layer peeling and erosion occurred at an impact angle of 30°. Additionally, impact crater depths at a 90° angle and impact speeds ranging from 1 to 20 m/s varied between 0.66 and 4.25 μm, with crater depths showing a correlation to the thickness of the oxide layer. Concurrently, in-situ measurements of the impact crater healing process during heating revealed that the crater formed at a 30° impact angle, which had numerous microcracks, exhibited significantly better healing compared to the crater formed at a 90° impact angle. The thickening process of the oxide layer were also analyzed, leading to the derivation of the oxide layer growth kinetic equation based on the measurement data: . This study is the first to use DH technology to measure the surface morphology of steel and to conduct in-situ analysis of the oxide layer thickening process following particle impact and during heating. This approach provides a novel perspective for understanding the erosion-oxidation interaction mechanism.

Automatic detection of temporomandibular joint osteoarthritis radiographic features using deep learning artificial intelligence. A Diagnostic accuracy study

ObjectiveThe purpose of this study was to investigate the diagnostic performance of a neural network Artificial Intelligence model for the radiographic confirmation of Temporomandibular Joint Osteoarthritis in reference to an experienced radiologist. Materials and MethodsThe diagnostic performance of an AI model in identifying radiographic features in patients with TMJ-OA was evaluated in a diagnostic accuracy cohort study. Adult patients elected for radiographic examination by the Diagnostic Criteria for Temporomandibular Disorders decision tree were included. Cone-beam computed Tomography images were evaluated by object detection YOLO deep learning model. The diagnostic performance was verified against examiner radiographic evaluation. ResultsThe differences between the AI model and examiner were non-significant statistically, except in the subcortical cyst (P=0.049*). AI model showed substantial to near-perfect levels of agreement when compared to those of the examiner data. Regarding each radiographic phenotype, the AI model reported favorable sensitivity, specificity, accuracy, and highly statistically significant Receiver Operating Characteristic (ROC) analysis (p < 0.001). Area Under Curve ranged from 0.872, for surface erosion, to 0.911 for subcortical cyst. ConclusionAI object detection model could open the horizon for a valid, automated, and convenient modality for TMJ-OA radiographic confirmation and radiomic features identification with a significant diagnostic power.

An unresolved SPH-DEM model for simulation of ductile and brittle surface erosion by abrasive water-jet (AWJ) impact

The abrasive water-jet (AWJ) erosion process involves the complex interaction between fluid medium, abrasive particles and solid material, which brings great challenges to the establishment of numerical model. Because traditional grid-based methods are not suitable for the problems of local deformation and material removal, the meshfree method smoothed particle hydrodynamics (SPH), based on the unresolved coupling and the discrete element method (DEM), is adopted to establish the model for AWJ study. The fluid medium is treated as a weakly compressible viscous liquid, the solid material is treated as an elastic-plastic material, and the abrasives are treated as rigid bodies. The fluid and solid phases are discretized with SPH particles, and the abrasives are described with DEM particles. The Johnson-Cook (J-C) and Johnson-Holmquist-II (JH-2) constitutive models are used to describe the stress-strain behavior of ductile and brittle materials, respectively. The effectiveness of the numerical model is further verified by AWJ impact experiments. The plastic deformation and cumulative failure characteristics of ductile materials, and the crack formation and propagation characteristics of brittle materials are systematically analyzed. The results provide insight for the AWJ research and lay a foundation for investigation of other complex fluid-particle flow in a numerical way.

The Cross-Verification of Different Methods for Soil Erosion Assessment of Natural and Agricultural Low Slopes in the Southern Cis-Ural Region of Russia

The conventional measuring methods (runoff plots and soil morphological comparison) and models (WaTEM/SEDEM and regional model of Russian State Hydrological Institute (SHI)) were tested with regard to the Southern Cis-Ural region of Russia, along with data from rainfall simulation for assessing soil erosion. Compared with conventional methods, which require long-running field observations, using erosion models and rainfall simulation is less time-consuming and is found to be fairly accurate for assessing long-term average rates of soil erosion and deposition. In this context, 137Cs can also be used as a marker of soil redistribution on the slope. The data of soil loss and sedimentation rates obtained by using conventional measuring methods were in agreement with the data based on the used contemporary modeling approaches. According to the erosion model calculations and data on the fallout of radionuclides in the Southern Cis-Ural (54°50–25′ N and 55°44–50′ E), the average long-term annual soil losses were ~1.3 t·ha−1 yr−1 in moderate (5°) arable slopes and ~0.2 t·ha−1 yr−1 in meadows. In forests, surface erosion is negligible, or its rates are similar to the rate of soil formation of clay–illuvial chernozems. The rates of soil erosion and sediment deposition on the arable land obtained using different methods were found to be very close. All the methods, including the WaTEM/SEDEM, allowed us to measure both soil erosion and intra-slope sedimentation. The regional SHI model fairly accurately assesses soil erosion in the years when erosion events occurred; however, soil erosion as a result of snowmelt did not occur every year, which should be taken into account when modeling. The concentrations of 137Cs in the topsoil layer (0–20 cm) varied from 0.9 to 9.8 Bq·kg−1, and the 137Cs inventories were 1.6–5.1 kBq·m−2, with the highest values found under the forest. The air dose rate in the forest was higher than in open areas and above the average of 0.12 μSv·h−1 on the slope (0.1 μSv·h−1 in the meadow and 0.08 μSv·h−1 on the arable land), with the value increasing from the watershed to the lower part of the slope in all the areas. The γ-background level in the studied ecosystems did not exceed the maximum permissible levels.

Elucidation of spacecraft surface wear phenomena in the plasma environment emitted by electric propulsion vehicles based on spacecraft charging analysis

Professor Takanobu Muranaka, Chukyu University, Japan, is part of a collaborative research effort to investigate and elucidate surface wear phenomena in electric propulsion spacecraft vehicles. He and his team are exploring how injected plasma emitted by these vehicles interacts with the spacecraft, leading to potential electrical and mechanical issues. For example, the ions and electrons in the plasma can collide with the spacecraft, causing wear and tear. This can compromise the spacecraftâ–™s durability and lifespan. In order to analyse these interactions, Muranaka and the team are utilising numerical calculations. To overcome limitations associated with the analysis of spacecraft systems and plasma in space, the researchers perform analyses of objects under predetermined conditions without consideration of space or timescales. Although it isnâ–™t possible to fully replicate space conditions in ground-based vacuum chambers, in their analyses the researchers are able to obtain important raw measurement data on physical phenomena that have not been modelled, such as parameter measurements of electrically propelled plasma plumes. Through its research, the team hopes to contribute to spacecraft design by informing design parameters such as the spacecraft shape and thruster parameters. Ultimately, the researchers are expanding and verifying numerical models and developing advanced plasma interference analysis technologies that will prove invaluable to spacecraft design. The researchers’ investigations on the Hayabusa2 spacecraft’s side-cathode ion thruster system have yielded exciting results on the ion energy distribution function (IEDF) of backflowing ions at multiple points around this thruster, expanding their findings on the significance of thruster reference potential on ion energy distribution, which is key to understanding spacecraft surface erosion.

Impact of Rainfall and Soil Infiltration on Groundwater Dynamics of Yerekoppi-1 Micro-watershed, Haveri District, Karnataka, India

The amount of water infiltrating the soil surface directly affects the quantity of surface runoff and erosion, and the recharge of both soil and groundwater. Groundwater recharge is an informative indicator of the water located beneath the ground surface. It has a direct impact on renewable supplies of groundwater. In the present study on Impact of rainfall and soil infiltration rate was used for effect on the groundwater level of the Yerekoppi-1 micro watershed (Manakur sub-watershed) in Haveri district of Karnataka state. Average annual rainfall is 700.7 mm and mean potential evapotranspiration is 1541.8 mm. An area of about 888 ha (94.32 %) has clay texture at the surface and 53 ha (5.68%) area has contributing settlement. In Yerekoppi-1 micro- watershed, 38 borewells are there in the vicinity of major stream of the micro- watershed. The mean depth of groundwater levels in the micro- watershed were monitored at a monthly frequency during January-2023 to March-2024. It was found that the maximum average depth of bore wells are about 17.6 mbgl and lowest average depth of borewell about 8.8 mbgl. Soil infiltration rate was measured at upper, middle and lower reaches of the watershed area in the year 2023 and 2024. The majority of the area contributed clay soil. In all the areas of micro-watershed, infiltration rate for clay soil is less than 5 mm/hr. Infiltration rates for all the areas was 1.72- 4.78 mm/hr. Soil infiltration during a rainstorm is closely related to a number of factors such as the intensity and kinetic energy of the rainfall, soil surface conditions and soil properties such as those related to aggregate stability. The groundwater recharge may be improved by growing plantation crop for increasing infiltration rate, construction of percolation tanks and farm ponds in the lower most of the agricultural land.

Coupled CFD-DEM modeling of surface erosion in granular soils: Simulation of erosion function apparatus experiments

This study introduces a numerical modeling approach that couples the computational fluid dynamics (CFD) with the discrete element method (DEM) to simulate grain-scale soil erosion processes induced by water flows. In this modeling framework, CFD simulates fluid flows by solving the volume-averaged Navier-Stokes equations, and uses the k-ω turbulent model for turbulent flows. Simultaneously, DEM computes the displacement of solid particles by incorporating the fluid-particle interactions driven by fluid flows while adhering to Newton's laws of motion. These interactions encompass drag force, buoyancy force, pressure-gradient force, and viscous force exerted by fluid flows and acting on the particles. The coupled CFD-DEM modeling adeptly replicates soil erosion processes, demonstrating good alignment with results obtained from laboratory erosion function apparatus (EFA) tests. In particular, the DEM facilitates the estimation of shear stress acting on the soil surface based on fluid-particle interaction forces, which has been roughly approximated by empirical or semi-empirical models. This study underscores the capability of coupled CFD-DEM in providing valuable insights into the grain-scale behavior of soil particles subjected to fluid flows, with the potential for extension to address soil erosion and fines migration.

Enormous headward and gully erosion in a floodplain area reclaimed for open-cast lignite mining during the July 2021 flood in the Inde River valley (Western Germany)

BackgroundThe July flood 2021 at the mountain front of the Eifel-Ardennes Mountains and their foreland resulted in the flooding of the lignite mining area of Inden in Germany. The mining activities resulted in large-scale anthropogenic changes to the relief and fluvial system, leading to a landscape that is no longer adjusted to the recent process-response system. This paper concentrates on the Inde River, where lignite mining led to the relocation of a 5-km-long river section. The flood event resulted in the temporary avulsion of the Inde River into the former channel and, ultimately, in the flooding of the open-cast lignite mine Inden.ResultsThe flooding of the open-cast lignite mine Inden led to headwall erosion and enormous sediment mobilisation, mobilising more than half a million cubic metres of sediment within a few hours, forming a 700-m-long deeply incised channel cut. Thereby, the underlying bedrock, near-subsurface man-made structures, and former river channels influence the erosional processes to different degrees. Surface erosion is likely to be the decisive process, and subsurface erosion is likely to play a secondary role. In both cases, former channels and mill ditches were likely impacting the course of erosional processes.ConclusionsDuring high flood events open-cast mining sites in floodplains are endangered by enormous erosion and sediment transport within a short period of time (several hours). Understanding such complex erosion and depositional processes in open-cast mining areas could provide a blueprint for geomorphological processes and hazards in these anthropogenically shaped fluvial landscapes. Further, information on historic impact in the area is crucial to estimate potential risks.

Fermented Soymilk with Probiotic Lactobacilli and Bifidobacterium Strains Ameliorates Dextran-Sulfate-Sodium-Induced Colitis in Rats.

Background: Current treatments for inflammatory bowel disease (IBD) are relatively futile and the extended use of drugs may reduce effectiveness. Several probiotic strains have shown promise in relieving/treating IBD symptoms. Objectives: The current study investigated the impact of fermented soymilk with a mixture of probiotic starter cultures containing Lactobacillus rhamnosus, L. casei, L. plantarum, L. acidophilus, Bifidobacterium longum, and B. animalis subsp. lactis in rats with dextran sulfate sodium (DSS)-induced colitis compared to control. Methods: Rats were randomly assigned to five groups (5 rats/group; n = 25): G1: negative normal control; G2: positive control (DSS); G3: DSS with sulfasalazine (DSS-Z); G4: DSS with soymilk (DSS-SM), and G5: DSS with fermented soymilk (DSS-FSM). Parameters monitored included the following: the disease activity index (DAI), macroscopic and histological assessments of colitis, and a fecal microbial analysis performed to assess the severity of inflammation and ulceration. Results: The DSS-FSM rats group exhibited lower DAI scores (p < 0.05) than other treated groups during the induction period. A macroscopical examination revealed no ulceration or swelling in the intestinal mucosa of rats in the DSS-FSM-treated group, resembling the findings in the negative control group. In the positive control (DSS group), the colon tissue showed increased inflammation (p < 0.05), whereas those in the DSS-SM- and DSS-FSM-treated rats groups did not show significant macroscopic scores of colitis. The positive DSS control and DSS-Z groups had crypt erosion and ulceration areas, severe crypt damage, and epithelial surface erosion, which were absent in the negative control and DSS-FSM groups. The counts of Lactobacillus spp. and Bifidobacterium spp. remained stable in both G1 and G5 over 4 weeks. The consumption of fermented soymilk with a mixture of probiotics could minimize the severity of DSS-induced colitis in rats. Conclusion, it was found that fermented soymilk containing Lactobacilli and Bifidobacterium might be an effective vehicle for reducing the severity of DSS-induced colitis in rats.

Unravelling biochemical and molecular mechanism of a carboxylesterase from Dietzia kunjamensis IITR165 reveal novel activities against polyethylene terephthalate

Plastics and plasticizers accumulate in the ecological niches affecting biodiversity, and human and environmental health. Bacteria degrading polyethylene terephthalate (PET) were screened and PETases involved in PET degradation were characterized. Here, we identified a carboxylesterase Dkca1 of 48.44 kDa molecular mass from Dietzia kunjamensis IITR165 shown to degrade amorphous PET film into bis(2-hydroxyethyl) terephthalate (BHET) and terephthalic acid (TPA) formed 64.35 μM and 35.26 μM, respectively within 96 h at 37 °C as revealed by LC-MS analysis showed significant PET hydrolase activity similar to reported PETases. SEM analysis confirms the surface erosion as cavities and holes. Dkca1 also hydrolysed BHET and dibutyl phthalate (DBP) at a concentration of 1 mM within 3 h indicating its versatility. Fluorescence quenching shows Dkca1 protein has a maximum affinity (Kd) towards BHET (86.55 μM) than DBP (134.2 μM). The protein demonstrated high stability under temperatures above 40 °C and at the pH range of 6.0–9.0. Moreover, Amino acid composition showed that the Dkca1 enzyme belongs to family VII carboxylesterase containing conserved catalytic triad of Ser183-Glu289-His378 with pentapeptide motif GXSAG and an oxyanion hole H103GGG106, sharing 37.47 % and 32.44 % similarity with a PET hydrolase TfCa from Thermobifida fusca and PAE hydrolase CarEW from Bacillus sp. K91, respectively. A docking study revealed that ligand PET, BHET, and DBP showed favourable binding in the catalytic pocket of the Dkca1 protein.

Analysis of Erosion of Surfaces in Falling Particle Concentrating Solar Power

Abstract Next generation concentrating solar power (CSP) systems, which utilize solid particles for energy capture, transport, and storage, offer prospects for higher temperature operation, improved efficiency, and reduced overall costs. Nevertheless, the continuous impingement of particles on component materials can result in substantial erosion, significantly constraining the performance and longevity of the components. A comprehensive understanding of particle erosion on surfaces is essential for designing components and operational parameters or coatings that minimize wear. This study presents a computational physics-based particle tracking model of the erosion rate of incident surfaces under different geometric, operational, and particle parameters. The computational model is validated with experimental measurements conducted as part of the study. Computational simulations are presented to elucidate the effects of each parameter and further used to investigate erosion rates in a systematic design of experiments covering a wide range of parameters. Based on the simulation results, a generalized analytical model is developed to relate erosion wear to pertinent dimensionless groups governing the physics of the process. The analytical model is shown to be accurate to within 10% and its use in understanding surface erosion as well as designing wear-resistant coatings to limit erosion within acceptable values is presented.

Insights into the relationship between particulate flow characteristics and local erosion behaviour under waterjet: The role of particle-fluid-surface interaction

In this study, the erosion characteristics of eutectic high entropy alloy under the liquid–solid two-phase flow is investigated by a coupled numerical-experimental method, in order to reveal the intrinsic relationship between microscopic erosion mechanism (experimental test) and the related particle-fluid-surface interaction (CFD modelling). Furthermore, instead of the common relation between average erosion rate and mainstream flow velocity, the relationship between local erosion distribution and local particulate flow characteristics is clarified. The erosion rate and erosion pattern match well between the experiment and simulation. The results demonstrate that NiCoCrFeNb0.45 exhibits superior anti-erosion performance when compared to other widely used equipment metals. The erosion profile agrees well with the shape of surface velocity distribution, indicating a close relationship between surface erosion behaviour and flow characteristics. In particular, the erosion pattern at a normal angle appears as a symmetric ring due to the flow stagnation phenomenon, with slight erosion damage in the centre area and severe erosion in the surrounding, whereas the erosion profile at an oblique angle displays an elliptic shape, with severe erosion damage in centre. Notably, the primary erosion mechanism varies dramatically in different surface regions, induced by the various impact velocities and angles associated with the corresponding changes in the flow field. This study provides a deeper understanding of erosion behaviour in terms of the interrelationship among the material mechanical properties, particulate flow field and particle-surface impingement behaviour.

Laboratory Model Tests on the Deformation and Failure of Terraced Loess Slopes Induced by Extreme Rainfall

Heavy rainfall is the main factor inducing the failure of loess slopes. However, the failure mechanism and mode of terraced loess slopes under heavy rainfall have not been well investigated and understood. This paper presents the experimental study on the deformation and failure of terraced loess slopes with different gradients under extreme rainfall conditions. The deformation and failure processes of the slope and the migration of the wetting front within the slope during rainfall were captured by the digital cameras installed on the top and side of the test box. In addition, the mechanical and hydrological responses of the slope, including earth pressure, water content, pore water pressure, and matric suction, were monitored and analyzed under rainfall infiltration and erosion. The experimental study shows that the deformation and failure of terraced loess slopes under heavy rainfall conditions exhibit the characteristic of progressive erosion damage. In general, the steeper the slope, the more severe the deformation and failure, and the shorter the time required for erosion failure. The data obtained from sensors embedded in the slope can reflect the mechanical and hydraulic characteristics of the slope in response to rainfall. The earth pressure and pore water pressure in the slope exhibit a fluctuating pattern with continued rainfall. The failure mode of terraced loess slopes under extreme rainfall can be summarized into five stages: erosion of slope surface and formation of small gullies and cracks, expansion of gullies and cracks along the slope surface, widening and deepening of gullies, local collapse and flow-slip of the slope, and large-scale collapse of the slope. The findings can provide preliminary data references for researchers to better understand the failure characteristics of terraced loess slopes under extreme rainfall and to further validate the results of numerical simulations and analytical solutions.

Computational Fluid Dynamics Study of Erosion on 900 MW Steam Turbine ND-45 Blades Using 3D Scanning.

This paper presents a comprehensive study on the impact of erosion on the flow characteristics through the blade of the last stage of a 900 MW steam turbine. The primary objective is to understand how surface erosion, caused by prolonged steam exposure, affects flow behavior and the overall efficiency of a 900 MW class turbine. The research process began with a 3D scan of the turbine blade, using advanced laser scanning technology to create a detailed geometric model. As one of the longest blades used in steam turbines, it posed both a technical challenge and was an innovative aspect of this study. The resulting 3D model served as the basis for numerical simulations using Computational Fluid Dynamic (CFD) methods, which allowed for the analysis of steam flow over the eroded blade surface. Key flow parameters, including velocity, pressure, and turbulence, were assessed to determine the impact of erosion. The study revealed significant changes in flow characteristics depending on the degree of erosion, providing valuable insights for turbine optimization and maintenance. The novelty of this research lies not only in the use of advanced scanning technologies but also in analyzing one of the longest blades in industrial practice, with findings that could enhance turbine efficiency and inform new erosion risk management strategies.

Microstructure and surface properties of Co-based brazed alloys coatings

Abstract The paper investigates the characteristics of two different manufactured high temperature brazed coatings using a cobalt based powder applied onto the surface of a stainless-steel substrate (AISI 904L). The coatings are intended to shield components exposed to high temperatures in an atmosphere where wear is expected. Energy dispersive analysis (EDX) together with scanning electron microscopy (SEM) was used to characterise the coating microstructure and morphology, and X-ray diffraction was used to identify the phase composition. Properties evaluations were carried out on the coatings’ surface characteristics, including hardness, erosion behaviour and hot corrosion resistance. The hot corrosion test was conducted at 650°C in a salt mixture that contained 75 wt. % sodium sulphate (Na2SO4) and 25 wt.% sodium chloride (NaCl). Alumina particles were used in the erosion tests, which hit the samples surface with an impact angle of 90°.The degree of corrosion attack, erosion behavior and hardness depended on the microstructure of the manufactured vacuum brazed coatings.

The effect of roughness and top layer in solid particle impingement erosion of multilayer nanostructured nitride PVD coatings

The effect of the surface roughness of the coating and the composition of the upper layer on the solid particle erosion of multilayer nanostructured coatings applied via cathodic arc evaporation (CAEPVD) method was investigated. CrN/TiN nanostructured multilayer coating (TiN as the upper layer) and TiN/CrN nanostructured multilayer coating (CrN as the upper layer) were applied on 410 stainless steel through the CAEPVD method with the following architecture. 1) a bottom layer of Cr and CrN deposited on the substrate, 2) nanolayers of TiN and CrN deposited on the bottom layer alternately and 3) an upper layer of CrN or TiN deposited on the nanolayers. After applying the coating, half of the samples were polished to obtain smooth surfaces, while the other half remained unpolished, resulting in rough surfaces. Surface morphology, phases identification, adhesion, mechanical, and erosion behavior of the coatings were characterized using SEM, XRD, Rockwell adhesion measurements, nanoindentation test, and solid particle impingement, respectively. The nano-scale indentation results demonstrated that the hardness, Young's modulus, H/E, and H3/E2 of the CrN/TiN coating were 5.57, 1.42, 3.86, and 85.39 times larger than those of the substrate. For the TiN/CrN coating, the values were 4.04, 1.13, 3.53 and 51.68 times greater than those of the substrate. The results of the erosion test showed that the erosion mass loss for the CrN/TiN and TiN/CrN coatings decreased up to 73% and 67%, respectively. Additionally, surface smoothing improved erosion resistance by 40% for both coatings. This shows that the smoothed CrN/TiN nanostructured multilayer coating is an excellent candidate for increasing the erosion resistance due to the higher ratios of H/E and H3/E2 and smoother surface.